TT virus DNA in serum, peripheral blood mononuclear cells and semen of patients infected by HIV

A number of recent studies [1–4] have reported on the parenteral transmission of TT virus (TTV), and some have studied the virus in HIV-infected patients [5]. Although some authors associate TTV with liver disease [1,2,6,7], others have not been able to demonstrate significant liver damage caused by the virus. TTV thus has no clear association with disease [4,8,9]. The presence of TTV was investigated in 70 serum samples from HIV-infected patients from southern Spain [52 men, 18 women; mean age: 36.47 ± 9.71 years; risk factors: 46 intravenous drug users (IVDU), five heterosexuals; eight homosexuals, 11 unknown; seven hepatitis B virus surface antigen (HBsAg) positive, 37 anti-hepatitis C virus (HCV) positive and 24 RNA-HCV positive; mean alanine aminotransferase (ALT): 83 ± 92; mean aspartate aminotransferase (AST): 66 ± 77; mean CD4 cells/μl: 428 ± 277; mean viral load copies/ml: 35 108 ± 130 118]. The control group consisted of 100 patients in whom liver disease had been excluded, all undergoing routine outpatient medical examinations (no IVDU, 51 men and 49 women; mean age: 35.53 ± 10.49; three HBsAg positive and none anti-HCV or anti-HIV positive; mean ALT: 19 ± 9; mean AST: 18 ± 7). TTV DNA detection involved a single tube assay using semi-nested polymerase chain reaction [2]; the presence of TTV in peripheral blood mononuclear cells (PBMC) and semen were also determined. Genotyping was by restriction fragment length polymorphism (RFLP) [10] and confirmed by DNA sequencing in a representative sample [11]. The genetic relationship between isolates was studied by single-stranded conformation polymorphism. TTV was detected in 2% of our Spanish control population, a figure similar to that reported elsewhere in Europe and the USA [3,12]. In contrast, 16% of our HIV-infected patients had TTV. TTV DNA detection was not related to repeated parenteral drug use: although 64% of the TTV-positive patients were IVDU, 66% of the patients who were negative for TTV DNA were also IVDU. Moreover, the mean time in years of intravenous drug use was not significantly different for the TTV-positive and negative groups. This may be because serum TTV titres are very low; if the amount of blood inoculated cannot harbour infectious doses of TTV, needle-sharing would not be a means of transmitting the virus [5]. As shown in Table 1, there was no relationship between TTV DNA detection and transaminase levels, or sex, age, HCV and hepatitis B virus infection, past infection by hepatitis A virus, levels of γ-glutamyl transferase, alkaline phosphatase, HIV category, CD4 cell count, viral load or treatment with lamivudine.Table 1: Epidemiological, immunological and virological characteristics of HIV-infected patients in association with the presence of TTV DNA. Very little information about the sexual transmission of TTV is available. A study of HIV-positive and negative homosexuals and prostitutes [5] suggested that this mode of transmission was improbable. An analysis of semen or vaginal fluids would have allowed an investigation of the possibility of this mode of transmission; unfortunately, only three patients gave written consent for the study of TTV in semen specimens. All three of these patients were positive for TTV DNA in PBMC, and the patient with the highest TTV serum titre also harboured it in his semen. Genetic analysis of the three isolates by single-stranded conformation polymorphism revealed that the same TTV strain was in the serum, PBMC and, when detectable, also in the semen. To date, ours is the only study documenting the presence of TTV DNA in semen. However, if TTV can be detected in the semen of infected patients, it follows that sexual transmission is feasible. This finding points to the need to address many related issues, such as the amount of TTV in the semen, and the capability of the virus to be transmitted sexually, which is known to be enhanced for other viruses in HIV patients. There is little information available on TTV genotype distribution in southern Spain or in HIV-infected patients. Our study found genotype 1 (G1) in the two TTV-positive patients from the control group and in three HIV patients. Genotype 2 (G2) was seen in four HIV patients, and three HIV patients showed a mixed RFLP pattern with both G1 and G2. One patient who could not be genotyped by RFLP was sequenced as a mixture of viruses belonging to G1 and G2. No association was found between the TTV genotype and intravenous drug use among HIV-infected patients. Our study shows that TTV is found more frequently in HIV-infected patients than in non-infected controls, although no relationship with IVDU practice was observed. Most noteworthy is the detection of TTV DNA sequences in the semen of a patient co-infected by HIV and TTV. We believe these findings will contribute to a better understanding of this newly described virus, although there is clearly a need for further epidemiological studies to assess the risks of the sexual transmission of TTV. Nora M. Martíneza Federico Garcíaa Fernando Garcíaa Marta Álvareza María C. Bernala Gonzalo Piédrolaa José Hernándezb María C. Marotoa